#11804: delta_qexp() fails in large characteristic
--------------------------------+-------------------------------------------
Reporter: jdemeyer | Owner: AlexGhitza
Type: defect | Status: new
Priority: major | Milestone: sage-4.7.2
Component: basic arithmetic | Keywords: FLINT NTL polynomial
_mul_short _mul_trunc delta_qexp _delta_poly_modulo
Work_issues: | Upstream: N/A
Reviewer: | Author:
Merged: | Dependencies:
--------------------------------+-------------------------------------------
Sage fails to compute the q-expansion of the Delta modular form in large
(>= machine word) characteristic:
{{{
sage: R = IntegerModRing(5^100)
sage: delta_qexp(200, 'q', R)
Exception OverflowError: 'long int too large to convert' in ignored
---------------------------------------------------------------------------
OverflowError Traceback (most recent call
last)
/home/jdemeyer/<ipython console> in <module>()
/usr/local/src/sage-4.7.1/local/lib/python2.6/site-
packages/sage/modular/modform/vm_basis.pyc in delta_qexp(prec, var, K)
389 ch = K.characteristic()
390 if ch > 0 and prec > 150:
--> 391 return R(_delta_poly_modulo(ch, prec), prec, check=False)
392 else:
393 # compute over ZZ and coerce
/usr/local/src/sage-4.7.1/local/lib/python2.6/site-
packages/sage/modular/modform/vm_basis.pyc in _delta_poly_modulo(N, prec)
307
308 P = PolynomialRing(Integers(N), 'q')
--> 309 f = Polynomial_zmod_flint(P, x=v, check=False)
310 t = verbose('made series')
311 # fast way of computing f*f truncated at prec
/usr/local/src/sage-4.7.1/local/lib/python2.6/site-
packages/sage/rings/polynomial/polynomial_zmod_flint.so in
sage.rings.polynomial.polynomial_zmod_flint.Polynomial_zmod_flint.__init__
(sage/rings/polynomial/polynomial_zmod_flint.c:11069)()
/usr/local/src/sage-4.7.1/local/lib/python2.6/site-
packages/sage/rings/polynomial/polynomial_zmod_flint.so in
sage.rings.polynomial.polynomial_zmod_flint.Polynomial_template.__init__
(sage/rings/polynomial/polynomial_zmod_flint.c:5301)()
/usr/local/src/sage-4.7.1/local/lib/python2.6/site-
packages/sage/rings/polynomial/polynomial_zmod_flint.so in
sage.rings.polynomial.polynomial_zmod_flint.get_cparent
(sage/rings/polynomial/polynomial_zmod_flint.c:2599)()
OverflowError: long int too large to convert
}}}
--
Ticket URL: <http://trac.sagemath.org/sage_trac/ticket/11804>
Sage <http://www.sagemath.org>
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